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Stimulated Raman scattering (SRS) of OH stretching vibrations in pure water and dilute ethanol–water solutions under different pump laser energies has been investigated using Nd:YAG laser. Two characteristic peaks at about 3252 and 3390 cm−1 are observed in mixture solutions, indicating the formation of strong and weak hydrogen bonds in water. A new shoulder peak at 3350 cm−1 appears in the mixture solutions at high laser energy due to the enhancement of hydrogen bond structure of water molecules. Simultaneously, the normalized SRS intensity of mixture solutions is higher than that of pure water at the same laser energy. These results indicate that SRS of water molecules is enhanced in dilute ethanol–water solutions. We propose that the mechanism is the reduction of the laser breakdown threshold of liquid water via ethanol, resulting in a strong nanoshock wave, thereby enhancing the SRS of water. [ABSTRACT FROM AUTHOR]

Forward stimulated Raman scattering in pure water and H2O2–H2O mixture solutions are investigated under different pump laser energies. Three characteristic peaks are observed in mixture solutions due to the enhancement of hydrogen bonds (H‐bonds) structure of water molecules by H2O2. Simultaneously, stimulated Raman scattering lines indicate that high‐pressure ice‐phase is formed in mixture solutions, which is attributed to the reduction of the laser breakdown threshold of liquid water by H2O2, resulting in a strong dynamic high pressure. [ABSTRACT FROM AUTHOR]

Liquid water is a complex system consisting of ice‐like and quartz‐like structure based on the classic two‐state model. Although lots of theoretical work have been developed about this model, the experimental evidences are still needed. Herein, a 355‐nm pulse laser is employed to excite stimulated Raman scattering (SRS) of liquid water both in bulk and on surface, with the generation of shockwave‐induced dynamic high pressure. Two characteristic features Raman peaks of both spontaneous Raman and SRS indicate the coexistence of two structures in localized water area. The ice‐like structure corresponds to ice Ih phase under the presented conditions, because the pressure dependence behavior of Raman shift agree well with the anomaly of diffusion coefficient of ice Ih phase, when the shock wave‐induced dynamic high pressure forms. Two structures show different pressure‐dependent behaviors based on the SRS results; meanwhile, the distribution of two structures is different in bulk and on surface water. [ABSTRACT FROM AUTHOR]

Stimulated Raman scattering (SRS) in H2O2–H2O mixture solutions are obtained in forward and backward directions. Characteristic features peaks related to OH stretching vibrations of water are the appearance of three enhancement peaks in both directions. Simultaneously, the low‐wavenumber SRS peaks in water at 840 and 1,700 cm−1 are enhanced. The mechanism of enhancement is attributed to excess electron‐enhanced Raman scattering. The electron‐enhanced process is also discussed. [ABSTRACT FROM AUTHOR]

Stimulated Raman scattering (SRS) spectra of the OH stretching vibrations of pure water and 2‐nm Si quantum dots (Si QDs) water solution have been investigated under different pump laser energies. Simultaneously, we have studied the spontaneous Raman spectra of pure water and Si QDs water solution at room temperature and atmospheric pressure. The results show that SRS intensity of Si QDs water solution is an order of magnitude higher than that of pure water at the same laser energy, which indicates that Si QDs enhance the SRS intensity of water molecules. The QDs enhancement SRS mechanism is attributed to the increase of third‐order nonlinear Raman susceptibility from the electric fields induced by the exciton effect of Si QDs. Stimulated Raman scattering (SRS) intensity of Si quantum dots (Si QDs) water solution is an order of magnitude higher than that of pure water.The increase of the third‐order nonlinear polarizability in water molecules is induced from the exciton effect of Si QDs.Due to Si QDs having a self‐absorption effect, the most obvious enhancement effect appears at laser energy of 110 mJ. [ABSTRACT FROM AUTHOR]